1. Field of the Invention
The present invention relates to a manufacturing method of a synthetic resin core material used in an extruded molding product such as a trim, a weather-strip or a window molding which is attached at a flange portion or the like of an opening portion in a vehicle body such as a door or a trunk of an automobile.
2. Description of the Related Art
In this type of extruded molding such as a trim, a weather-strip or a window molding used for holding a flange portion of an opening portion in a vehicle body such as a door or a trunk of an automobile, it is conventionally general to use a metallic core material in order to increase a holding force with respect to attachment of a vehicle body of an automobile
As a manufacturing method of this metallic core material, cut slot portions having various shapes are punched out in a state where they have a tabular cross section, and then a synthetic resin or a material such as rubber is extruded to a tabular core material having each cut slot portion to form a covering layer on both sides of the tabular core material. Thereafter, the tabular core material is bent and manufactured into a shape having a substantially U-like cross section.
Since environment issues are increasing in recent years, changing a material of a core from a metal to a synthetic resin has been demanded in order to achieve a reduction in weight of the core material and recycling.
However, when the synthetic resin core material is manufactured from a flat plate like a metallic core material, there is a problem that bending the core material into a shape having a substantially U-like cross section is very difficult.
Further, cut slot portions having various shapes are formed by a press machine which operates in a vertical direction on a synthetic resin core material which has been extruded into a shape having a substantially U-like cross section in advance, but a speed of the press machine which operates in the vertical direction is slow, and hence there is a problem of poor manufacturing efficiency.
Therefore, it is mechanically very complicated and takes labors and time in a prior art to form a cut portion or a cut slot portion on opposed lateral sides of a U-shaped core material in order to readily bend in a three-dimensional direction a core material having a substantially U-like cross section consisting of a hard synthetic resin.